VK_EXT_debug_report

Other Extension Metadata

Last Modified Date

2020-12-14

IP Status

No known IP claims.

Contributors

Courtney Goeltzenleuchter, LunarG
Dan Ginsburg, Valve
Jon Ashburn, LunarG
Mark Lobodzinski, LunarG

Due to the nature of the Vulkan interface, there is very little error information available to the developer and application. By enabling optional validation layers and using the VK_EXT_debug_report extension, developers can obtain much more detailed feedback on the application’s use of Vulkan. This extension defines a way for layers and the implementation to call back to the application for events of interest to the application.

New Object Types

VkDebugReportCallbackEXT

New Commands

New Structures

Extending VkInstanceCreateInfo:
- VkDebugReportCallbackCreateInfoEXT

New Function Pointers

PFN_vkDebugReportCallbackEXT

New Enums

New Bitmasks

VkDebugReportFlagsEXT

New Enum Constants

VK_EXT_DEBUG_REPORT_EXTENSION_NAME
VK_EXT_DEBUG_REPORT_SPEC_VERSION
Extending VkObjectType:
- VK_OBJECT_TYPE_DEBUG_REPORT_CALLBACK_EXT
Extending VkResult:
- VK_ERROR_VALIDATION_FAILED_EXT
Extending VkStructureType:
- VK_STRUCTURE_TYPE_DEBUG_REPORT_CALLBACK_CREATE_INFO_EXT
- VK_STRUCTURE_TYPE_DEBUG_REPORT_CREATE_INFO_EXT

If Vulkan Version 1.1 is supported:

Extending VkDebugReportObjectTypeEXT:
- VK_DEBUG_REPORT_OBJECT_TYPE_DESCRIPTOR_UPDATE_TEMPLATE_EXT
- VK_DEBUG_REPORT_OBJECT_TYPE_SAMPLER_YCBCR_CONVERSION_EXT

Examples

VK_EXT_debug_report allows an application to register multiple callbacks with the validation layers. Some callbacks may log the information to a file, others may cause a debug break point or other application-defined behavior. An application can register callbacks even when no validation layers are enabled, but they will only be called for loader and, if implemented, driver events.

To capture events that occur while creating or destroying an instance an application can link a VkDebugReportCallbackCreateInfoEXT structure to the pNext element of the VkInstanceCreateInfo structure given to vkCreateInstance.

Example uses: Create three callback objects. One will log errors and warnings to the debug console using Windows OutputDebugString. The second will cause the debugger to break at that callback when an error happens and the third will log warnings to stdout.

    VkResult res;
    VkDebugReportCallbackEXT cb1, cb2, cb3;

    VkDebugReportCallbackCreateInfoEXT callback1 = {
        .sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CALLBACK_CREATE_INFO_EXT,
        .pNext = NULL,
        .flags = VK_DEBUG_REPORT_ERROR_BIT_EXT |
                 VK_DEBUG_REPORT_WARNING_BIT_EXT,
        .pfnCallback = myOutputDebugString,
        .pUserData = NULL
    };
    res = vkCreateDebugReportCallbackEXT(instance, &callback1, &cb1);
    if (res != VK_SUCCESS)
       /* Do error handling for VK_ERROR_OUT_OF_MEMORY */

    callback.flags = VK_DEBUG_REPORT_ERROR_BIT_EXT;
    callback.pfnCallback = myDebugBreak;
    callback.pUserData = NULL;
    res = vkCreateDebugReportCallbackEXT(instance, &callback, &cb2);
    if (res != VK_SUCCESS)
       /* Do error handling for VK_ERROR_OUT_OF_MEMORY */

    VkDebugReportCallbackCreateInfoEXT callback3 = {
        .sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CALLBACK_CREATE_INFO_EXT,
        .pNext = NULL,
        .flags = VK_DEBUG_REPORT_WARNING_BIT_EXT,
        .pfnCallback = mystdOutLogger,
        .pUserData = NULL
    };
    res = vkCreateDebugReportCallbackEXT(instance, &callback3, &cb3);
    if (res != VK_SUCCESS)
       /* Do error handling for VK_ERROR_OUT_OF_MEMORY */

    ...

    /* remove callbacks when cleaning up */
    vkDestroyDebugReportCallbackEXT(instance, cb1);
    vkDestroyDebugReportCallbackEXT(instance, cb2);
    vkDestroyDebugReportCallbackEXT(instance, cb3);

In the initial release of the VK_EXT_debug_report extension, the token VK_STRUCTURE_TYPE_DEBUG_REPORT_CREATE_INFO_EXT was used. Starting in version 2 of the extension branch, VK_STRUCTURE_TYPE_DEBUG_REPORT_CALLBACK_CREATE_INFO_EXT is used instead for consistency with Vulkan naming rules. The older enum is still available for backwards compatibility.

In the initial release of the VK_EXT_debug_report extension, the token VK_DEBUG_REPORT_OBJECT_TYPE_DEBUG_REPORT_EXT was used. Starting in version 8 of the extension branch, VK_DEBUG_REPORT_OBJECT_TYPE_DEBUG_REPORT_CALLBACK_EXT_EXT is used instead for consistency with Vulkan naming rules. The older enum is still available for backwards compatibility.

Issues

1) What is the hierarchy / seriousness of the message flags? E.g. ERROR > WARN > PERF_WARN …

RESOLVED: There is no specific hierarchy. Each bit is independent and should be checked via bitwise AND. For example:

    if (localFlags & VK_DEBUG_REPORT_ERROR_BIT_EXT) {
        process error message
    }
    if (localFlags & VK_DEBUG_REPORT_DEBUG_BIT_EXT) {
        process debug message
    }

The validation layers do use them in a hierarchical way (ERROR > WARN > PERF, WARN > DEBUG > INFO) and they (at least at the time of this writing) only set one bit at a time. But it is not a requirement of this extension.

It is possible that a layer may intercept and change, or augment the flags with extension values the application’s debug report handler may not be familiar with, so it is important to treat each flag independently.

2) Should there be a VU requiring VkDebugReportCallbackCreateInfoEXT::flags to be non-zero?

RESOLVED: It may not be very useful, but we do not need VU statement requiring the VkDebugReportCallbackCreateInfoEXT::msgFlags at create-time to be non-zero. One can imagine that apps may prefer it as it allows them to set the mask as desired - including nothing - at runtime without having to check.

3) What is the difference between VK_DEBUG_REPORT_DEBUG_BIT_EXT and VK_DEBUG_REPORT_INFORMATION_BIT_EXT?

RESOLVED: VK_DEBUG_REPORT_DEBUG_BIT_EXT specifies information that could be useful debugging the Vulkan implementation itself.

4) How do you compare handles returned by the debug_report callback to the application’s handles?

RESOLVED: Due to the different nature of dispatchable and nondispatchable handles there is no generic way (that we know of) that works for common compilers with 32bit, 64bit, C and C++. We recommend applications use the same cast that the validation layers use:

reinterpret_cast<uint64_t &>(dispatchableHandle)
(uint64_t)(nondispatchableHandle)

+ This does require that the application treat dispatchable and nondispatchable handles differently.

Version History

Revision 1, 2015-05-20 (Courtney Goetzenleuchter)
- Initial draft, based on LunarG KHR spec, other KHR specs
Revision 2, 2016-02-16 (Courtney Goetzenleuchter)
- Update usage, documentation
Revision 3, 2016-06-14 (Courtney Goetzenleuchter)
- Update VK_EXT_DEBUG_REPORT_SPEC_VERSION to indicate added support for vkCreateInstance and vkDestroyInstance
Revision 4, 2016-12-08 (Mark Lobodzinski)
- Added Display_KHR, DisplayModeKHR extension objects
- Added ObjectTable_NVX, IndirectCommandsLayout_NVX extension objects
- Bumped spec revision
- Retroactively added version history
Revision 5, 2017-01-31 (Baldur Karlsson)
- Moved definition of VkDebugReportObjectTypeEXT from debug marker chapter
Revision 6, 2017-01-31 (Baldur Karlsson)
- Added VK_DEBUG_REPORT_OBJECT_TYPE_DESCRIPTOR_UPDATE_TEMPLATE_KHR_EXT
Revision 7, 2017-04-20 (Courtney Goeltzenleuchter)
- Clarify wording and address questions from developers.
Revision 8, 2017-04-21 (Courtney Goeltzenleuchter)
- Remove unused enum VkDebugReportErrorEXT
Revision 9, 2017-09-12 (Tobias Hector)
- Added interactions with Vulkan 1.1
Revision 10, 2020-12-14 (Courtney Goetzenleuchter)
- Add issue 4 discussing matching handles returned by the extension, based on suggestion in public issue 368.